[RFA] Expand libgui to center on window

[Keith Seitz <keiths at cygnus dot com>]

Hi,

I'd like to expand libgui's center_window to allow windows to be centered
over another window (as well as centered on the screen).

Okay?
Keith

ChangeLog:
2001-05-18  Keith Seitz  <keiths@cygnus.com>

	* library/center.tcl (center_window): Allow centering
	the toplevel on a window, too.

Patch:
Index: library/center.tcl
===================================================================
RCS file: /cvs/src/src/libgui/library/center.tcl,v
retrieving revision 1.1.1.1
diff -u -p -r1.1.1.1 center.tcl
--- library/center.tcl	2000/02/07 00:19:47	1.1.1.1
+++ library/center.tcl	2001/05/18 21:05:37
@@ -1,13 +1,23 @@
-# center.tcl - Center a window on the screen.
-# Copyright (C) 1997, 1998 Cygnus Solutions.
+# center.tcl - Center a window on the screen or over another window
+# Copyright (C) 1997, 1998, 2001 Red Hat, Inc.
 # Written by Tom Tromey <tromey@cygnus.com>.

 # Call this after the TOPLEVEL has been filled in, but before it has
-# been mapped.  This proc will center the toplevel on the screen.
-proc center_window {top} {
+# been mapped.  This proc will center the toplevel on the screen or
+# over another window.
+proc center_window {top args} {
+  parse_args {{over ""}}
+
   update idletasks
-  set x [expr {int (([winfo screenwidth $top] - [winfo reqwidth $top]) / 2)}]
-  set y [expr {int (([winfo screenheight $top] - [winfo reqheight $top]) / 2)}]
+  if {$over != ""} {
+    set cx [expr {int ([winfo rootx $over] + [winfo width $over] / 2)}]
+    set cy [expr {int ([winfo rooty $over] + [winfo height $over] / 2)}]
+    set x [expr {$cx - int ([winfo reqwidth $top] / 2)}]
+    set y [expr {$cy - int ([winfo reqheight $top] / 2)}]
+  } else {
+    set x [expr {int (([winfo screenwidth $top] - [winfo reqwidth $top]) / 2)}]
+    set y [expr {int (([winfo screenheight $top] - [winfo reqheight $top]) / 2)}]
+  }
   wm geometry $top +${x}+${y}
   wm positionfrom $top user